Relationships between tree slenderness coefficients and stand characteristics for major plantation-grown species in North-western Nigeria

Abstract

This study established relationships between tree slenderness coefficient (used as an index of resistance of trees to windthrow) and some stand characteristics of three major tree species used for plantation establishment in some part of North-western Nigeria. Tree measurements for diameter at breast height (DBH) and total tree height were conducted on 60 randomly selected temporary sample plots (TSP) of 20 × 20 m, while tree slenderness coefficient (TSC), basal area (BA), and tree volume were computed from the field data. Pearson correlation was used to establish a relationship between TSC and other tree variables, while nonlinear regression analysis was used in developing models for predicting TSC from DBH and tree height. Results from descriptive statistics indicate that there were low slenderness coefficient values across the three species under study. TSC was found to be negatively correlated with tree DBH, BA, and volume but positively correlated with tree height. Five candidate models were selected as base models to predict TSC from DBH alone and result from the nonlinear regression analysis revealed that the exponential function produced better fit statistics and it was further modified to include an additional tree variable (height). Results of the regression model that includes additional tree variables have better fit statistics compared to those models (base models) without additional tree variables. An exponential function model is recommended for estimating TSC from DBH and tree height for the three major plantation-grown species in North-western Nigeria.